Development of sensory neurons, especially their pathfinding properties, will be analyzed in two insects; the house cricket Acheta dosmesticus in which embryonic neural development will be followed, and Drosophila melanogaster in which the adult nervous system that is laid down during metamorphosis will be similarly examined in homeotic mutants. Rules for sensory neuron projection to the central nervous system in these two very different insects will be related to emerging concepts of pattern formation and to relevant studies with vertebrates. Laser lesions of embryonic tissue in Acheta, and mutant stocks in Drosophila provide for experimental manipulation of the periphery and center. Cobalt and dye filling of axons, scanning and transmission electron microscopy will be used to determine the patterns neural connections in both species.